This should be an easier one; I remember this one fairly clearly.
Years ago I read a story where a team of explorers are exploring a planet. They have a mother ship as home base, and the mission is controlled by a highly intelligent computer.
Michael Target — the main character of the story — sets out to examine mysterious metal cylinders left by a previous race. I think he says there were around 200. They are long and thin as far as I can recall. He notices that they do not have dust on them, but they are lying in piles of dust. He takes the outer plates off of one of them, and photographs the inside.
Suddenly one of them tilts up, and Michael runs for cover. It shoots at him, destroying the air-creating apparatus which he wears on his back. He gets into a small cave beneath a boulder, but drops his camera in his dash. His back-pack which contains his replacement air machine is left behind outside.
All of the cylinders take off, and start flying (vertically I think) around his hiding place. The ship computer remarks that his file says he is a good marksman, and instructs him to shoot them near the nose. I remember it mentioning that his gun had a tubeless scope. When he shoots a cylinder, it just wobbles and resumes its circuit. They have two computer systems, so one would have to be shot twice for it to be destroyed.
Michael's ship's computer lies to him, telling him that it can see what is happening through his camera outside. In reality it does its best to calculate when the same cylinder come in range. Eventually one is hit twice, exploding and blinding all of the others. Michael, now oxygen-starved, gets out of his cave and retrieves his other air machine.
Back at his mother ship, Michael Target's friend jokes about "the Target that shot back".
There is a lot to go on, but I have not been successful in finding the story online. I read it in a book of short space stories, which included part of Out of the Silent Planet.
It also included a story about a family escaping from Earth which is wiped out by a war, and settling on Mars. In that story each boy got a city of their choice to live in.
There was also a story about a galactic trophy-hunter who shoots a huge, furry, sentient alien, but learns what he has done from others of its kind. He had a dog to help him.